Methods of making microelectronic packages utilizing coining

ABSTRACT

A package for a microelectronic element is made by making a microelectronic component, including embossing a metal sheet to form thin and thick regions, then etching or otherwise removing metal from the sheet in a nonselective removal process and arresting the removal process when the thin regions are removed but before the thick regions are removed. A base material may be applied to the metal sheet to form a dielectric layer for the component. The component is assembled with a microelectronic element to form the package.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Application Ser. No.60/032,721 filed Dec. 13, 1996 which is a continuation of U.S. patentapplication Ser. No. 08/989,587, filed Dec. 12, 1997, now U.S. Pat. No.6,083,837, the disclosures of which are both hereby incorporated byreference herein.

FIELD OF THE INVENTION

The present invention relates to methods of making microelectronicpackages and metallic parts and components for the same.

BACKGROUND OF THE INVENTION

Microelectronic packages include components for forming electricalconnections between microelectronic devices such as microelectronicchips or wafers and external circuitry. microelectronic packagescommonly incorporate conductive elements such as fine metallic leads andterminal structures disposed on a dielectric layer such as a polymericlayer. In conventional tape automated bonding or “TAB” a prefabricatedarray of leads is provided on a flexible dielectric tape. The leads arebonded to contacts on the microelectronic device. Certain embodimentsillustrated in U.S. Pat. Nos. 5,489,749; 5,518,964; 5,148,265;5,148,266, and 5,491,302 and International Publication WO 94/03036, thedisclosures of which are hereby incorporated by reference herein, alsoincorporate leads and other electrically conductive elements. Leads foruse with modern semiconductor chips having large numbers ofclosely-spaced contacts must be very fine. They may be about 20 to about40 microns wide. These leads must be provided in precise locations onthe connection component. Other components such as circuit panels alsoinclude fine metallic features such as conductors.

The metallic elements in these and other components have been fabricatedby various processes, most commonly by photochemical processes. In onephotochemical process, patternwise etching of a metallic layer isutilized to form the leads. A photographically patterned etch resist isused to selectively etch unwanted portions of the metal layer so thatthe resist-protected portions form the leads of the connectioncomponent. In another method, a metal is plated in areas defined by aphotographically patterned resist.

Photochemical processes suffer significant drawbacks in that theyrequire several steps. The resist must be exposed to illumination in thedesired pattern, typically by use of a mask. The resist is therebydeveloped so as to cure only the resist in exposed areas or only theresist in the unexposed areas. The uncured resist is then removed,leaving a mask which has openings in areas where metal is to be removedor added. After etching or plating, the cured resist forming the mask isthen removed. These steps entail significant cost and limit the speed offabrication. Electroplating produces unacceptable irregularities in themetal elements formed when performed too rapidly, also limiting thespeed with which the leads may be fabricated. In addition, photochemicalprocesses typically cannot form features smaller than a certain size.This size depends on the type of resist used and the developing process.

Conventional stamping processes have been used to fabricate relativelylarge metallic elements such as large leads. In a simple stampingprocess, a sheet of metal is passed between a pair of matched toolsreferred to as a punch and a die. The punch has a protrusioncorresponding to the shape of the part to be formed, whereas the die hasa hole precisely matched to the shape of the punch, and just slightlylarger than the punch. As the tools are forced together, the punchenters the hole in the die and shears a portion of the metal sheetcorresponding in shape to the punch from the remainder of the sheet. Invariants of these processes, the tools may perform additional operationssuch as bending the parts. Stamping processes can be performed rapidly.Although stamping processes can be used to form relatively large, coarseparts, it is typically not practical to stamp very fine leads for usewith microelectronic connection components having closely spacedcontacts.

Thus, despite the substantial time and effort expended to solve theproblems associated with fabrication of leads used in packagingmicroelectronic elements and other metallic parts, further improvementin such processes would be desirable.

SUMMARY OF THE INVENTION

The present invention improves upon processes for fabricating metallicparts such as the leads of microelectronic packages.

A method of packaging a microelectronic element in accordance with oneaspect of the present invention includes making one or moremicroelectronic components by embossing a layer of metal having a firstand a second face by engagement between a pair of forming elements,thereby deforming the metal layer into thick and thin regions. Embossingprocesses of this type are commonly referred to as “coining”, perhapsbecause these processes are similar to those used to form the raisedfeatures on coins. After the embossing or coining step, the thin regionsare then removed by a nonselective removal process acting on at leastone of the two faces of the metal layer. The nonselective removalprocess is halted before the thick regions of metal are removed, leavingthe thick regions of the metal layer as elements which constitute themetallic part. The component or components are assembled with one ormore microelectronic elements.

The embossing step may be performed on either or both faces of the metallayer. One or both of the forming elements have raised and recessedportions arranged so that the recessed portions are in the pattern ofthe desired conductive elements. The forming elements may be movedlinearly towards one another. Alternatively, one or both of the formingelements may be rollers, so that the metal layer is squeezed in a nipbetween the forming elements as the roller or rollers rotate.

The nonselective removal process may be performed on either or bothfaces of the metal layer, regardless of which face or faces areembossed. The nonselective removal process may be performed, forexample, by etching, reverse electroplating, sputtering or abrading themetal layer.

The embossing step may be performed at an extremely rapid rate, formingimpressions in the metal layer at production rates on the order of tensor hundreds of impressions per minute. The nonselective removal processcan also be performed rapidly, without the need for time-consuming stepssuch as selective exposure and development of a photoresist. Forexample, where the nonselective removal process involves etching orreverse electroplating, the entire layer is simply immersed in theetching or reverse electroplating solution and processed. An unlimitednumber of components can be subjected to the nonselective removalprocess simultaneously. Thus, even where the removal process requiressubstantial time, a high throughput rate can be maintained.

A process according to this aspect of the invention can be used to formextremely small conductive elements which are impractical to form usingmechanical processes such as conventional stamping. One limit on thesize of the conductive elements formed in processes according to thisaspect of the invention is the size of the raised and recessed portionswhich can be provided in the forming elements. However, the raised andrecessed portions in the forming elements may be formed by relativelyexpensive, precise processes without adding substantially to the cost ofthe finished product since the die is utilized repeatedly once shaped.

A method according to this aspect of the present invention may includethe step of forming a first layer of metal on the metallic elements. Forexample, certain preferred embodiments include the step of forming afirst layer of metal by electroplating onto the metallic elements alayer of metallic material different than the metallic material of themetallic elements. Certain preferred embodiments include forming asecond layer of metal on the metallic elements so that the first layerof metal comprises a layer of barrier material to prevent interdiffusionof metallic material between the metallic elements and the second layerof metal.

In certain embodiments, the one or more microelectronic components aremade in the form of a plurality of microelectronic components in acontinuous strip. The microelectronic components of the strip may beassembled with the one or more microelectronic elements to form acontinuous strip of assemblies. The assemblies may be severed from oneanother after being assembled.

In preferred embodiments, a base material is applied to the metal layerso as to form a coherent layer of the base material supporting themetallic elements. Certain preferred embodiments include forming one ormore apertures in the layer of base material in alignment with at leastsome of the metallic elements. The metallic elements may be formed aselongated leads and the apertures may be formed in alignment with theelongated leads so that the leads extend at least partially across theapertures. Certain preferred embodiments include forming thick regionsin the metal layer, including thick regions having different thicknessso that the removing step is arrested before the thinnest of the thickregions has been removed so that metallic elements left after thearresting step have different thicknesses. The one or more elongatedleads may be forced downwardly into one of the apertures which are inalignment with the elongated lead. In embodiments including thickregions having different thicknesses, the thinnest of the thick regionsmay include frangible sections so that the elongated leads may be forceddownwardly so as to break the frangible sections in the step ofassembling. The elongated leads may be bonded to contacts on the one ormore microelectronic elements.

Methods according to this aspect of the invention may form metallicelements which are releasable from a base material. The base materialmay comprise a dielectric material which does not form a strong bondwith the metallic material of the metal layer. The metallic elements mayinclude a first end fixed to the base material and a second end which isreleasable from the base material. A release-promoting material may beapplied to the metal layer prior to application of the base material.The base material may comprise a thermoplastic material applied bylimitation.

The steps of making one or more microelectronic components may beperformed so as to form the metallic elements as elongated leads. Spotsof a bondable alloy may be applied to the elongated leads. In certainpreferred embodiments, the spots of bondable material are appliedutilizing a patterned photo resist. The step of assembling may includebonding the spots of bondable material to contacts on the one or moremicroelectronic elements.

The step of embossing may be performed so that metallic elements havingan elongated portion, a tip end and a terminal end are formed, the tipend having a width greater than a width of the elongated portion. Thetip ends, in certain preferred embodiments, include tapering sides.Spots of bondable alloy may be applied to the tip ends of these metallicelements. The tip ends may be engaged with contacts of the one or moremicroelectronic elements, the contacts being in a pattern correspondingwith the tip ends, and the spots of bondable material may be bonded tothe contacts. The assembling step may further include moving the one ormore microelectronic components and the one or more microelectronicelements away from each other so that the tip ends are detached from thebase material.

The step of embossing may be performed to form metallic elements in anumber of different shapes. In certain embodiments, the step ofembossing forms cup-shaped features having an open end at the first faceof the metal layer and a closed end at the second face of the metallayer. The forming elements may include a first forming element having arecess and a second forming element having a projection in registrationwith the recess so as to form the cup-shaped features.

The step of embossing may also be performed so as to form acollar-shaped portion in the first face surrounding the open end of eachcup-shaped feature. The base material may be applied to the second faceof the metal layer so that the closed end of the cup-shaped feature isembedded in the layer of base material. Apertures may be formed in thebase material in alignment with the closed end of the cup-shapedfeature. The closed end may be electrically connected to the one or moremicroelectronic elements in the step of assembling.

Methods in accordance with this aspect of the present invention mayinclude utilizing selective removal processes. For example, additionalmetallic elements may be formed on a second face of the metal layer. Theadditional metallic elements may be formed utilizing a patternedphotoresist applied to the second face. The additional metallic elementsare preferably formed in contact with the metallic elements formed fromthe metal layer. A base material may be applied to the second face ofthe metal layer, overlying the additional metallic elements. Aperturesmay be formed, in certain preferred embodiments, in the base material inalignment with the additional metallic elements. The metallic elementspreferably have a width of less than 40 microns. A dielectric basematerial is applied, in certain preferred embodiments, to the first faceof the metal layer after the embossing step so that a coherentdielectric layer of the base material is adhered to the first face andintimately surrounds the protruding thick regions and so that the thickregions of the metal layer remain as conductive elements embedded in thedielectric base material after the arresting step.

Preferably, the base material is provided before the nonselectiveremoval step, so that conductive elements formed in that step remainembedded in or otherwise supported by the base material. The step ofapplying the base material may include applying a dielectric, such aspolyimide or similar materials. After the nonselective removal step, theresulting assembly can provide a connection component or otherelectronic part with conductive elements on a dielectric layer. Thedielectric may be applied by applying a flowable material to the metallayer, as by coating the metal layer with the flowable material, andthen curing the flowable material to form the dielectric. The step ofapplying the dielectric material may also include laminating a basematerial to the metal layer.

Apertures formed in the layer of base material may be used to provideaccess to the conductive elements. Alternatively or additionally, thebase material may include a metal having etching characteristicsdifferent from that of the metal layer from which the conductiveelements are formed. For example, the metal layer for forming theconductive elements may be comprised of copper and a different metalsuch as aluminum may be provided as a base material. After the embossingstep, the thin regions of the copper layer are etched to produce theconductive elements. Because the aluminum has etching characteristicsdifferent from those of copper, the aluminum layer is unaffected by theremoval process. The aluminum layer may then be removed by a causticetch or other process which leaves the copper conductive elements.

In a particularly preferred method according to this aspect of theinvention, one or more microelectronic components are formed. A firstface of the metal layer is embossed and a flowable polymer such as apolyimide is then applied to the first face of the metal layer by acoating process and cured to form a coherent polymer layer. Next, achemical etchant or reverse electroplating process nonselectivelyremoves metal from the second face of the metal layer to remove the thinregions of metal. The removal process is continued until the thinregions of metal are removed and the removal process is halted beforethe thick regions of metal are destroyed. After the removal process, thethick regions of metal remain embedded in the polyimide as theconductive elements of a microelectronic connection component. The oneor more microelectronic components are assembled with one or moremicroelectronic elements.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims and accompanying drawings where:

FIG. 1a is a partially perspective, partially block-diagrammatic view ofa process in accordance with one embodiment of the invention.

FIG. 1b is a diagrammatic bottom plan view of a forming element utilizedin a process of FIG. 1a.

FIG. 1c is a sectional elevational view on line 1 c—1 c in FIG. 1a,showing the forming element in conjunction with a metal layer andforming element used in the process of FIG. 1a.

FIG. 1d is a sectional view similar to FIG. 1b, at a later time in theprocess.

FIG. 1e is a sectional view of a metal layer and polymer layer at alater stage in the process of FIG. 1a.

FIG. 1f is a view similar to FIG. 1d, but taken at a later stage in theprocess of FIG. 1a.

FIG. 1g is a top plan view of the article at a still later stage of theprocess.

FIG. 2a is a diagrammatic bottom plan view of a forming element used ina process according to a further embodiment of the invention.

FIG. 2b is a sectional elevational view taken along the broken sectionline 2 b—2 b in FIG. 2a, showing the forming element in conjunction witha metal layer and another forming element used in the same process.

FIG. 2c is a sectional view similar to FIG. 2b but showing the elementsat a later time during the process.

FIG. 2d is a sectional elevational view of an article formed in theprocess of FIGS. 2a-2 c during a still later stage of the process.

FIG. 2e is a sectional view similar to FIG. 2d but showing the articleat a still later stage of the process.

FIG. 2f is a diagrammatic perspective view depicting a lead formed inthe process of FIGS. 2a-2 e.

FIG. 3a is a diagrammatic bottom plan view of a forming element used ina process according to yet another embodiment of the invention.

FIG. 3b is a sectional elevational view taken along line 3 b—3 b in FIG.3a, depicting the forming element in conjunction with a metal layer andanother forming element used in the same process.

FIG. 3c is a view similar to FIG. 3b but depicting the forming elementsand metal layer at a later time in the process.

FIG. 3d is a diagrammatic perspective view depicting a component formedin the process of FIGS. 3a-3 c.

FIG. 4a is a diagrammatic sectional elevational view depicting formingelements and a metal layer during a process in accordance with yetanother embodiment of the invention.

FIG. 4b is a sectional elevational view depicting the component formedin the process of FIG. 4a.

FIG. 5 is a fragmentary, diagrammatic sectional elevational viewdepicting forming elements and a metal layer during a process inaccordance with yet another embodiment of the invention.

FIG. 6 is a view similar to FIG. 5, but depicting forming elements and ametal layer in a process according to a further embodiment of theinvention.

FIG. 7 is a diagrammatic perspective view depicting an article during aprocess according to a further embodiment of the invention.

FIG. 8a is a fragmentary, diagrammatic sectional view depicting aforming element and metal layer during a process according to yetanother embodiment of the invention.

FIG. 8b is a view similar to FIG. 8a but depicting the metal during alater stage of the same process.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

A process for making microelectronic packages in accordance with oneembodiment of the present invention is illustrated by FIGS. 1a through 1g. This process uses a first forming element or die 13 and a secondforming element 14, also referred to as a backing element. Die 13 hasraised portions 18 and recessed portions 19 interspersed with the raisedportions. The recessed portions are disposed in a pattern correspondingto the pattern of conductive elements to be formed. FIG. 1b shows abottom plan view of a die having one such pattern of raised and recessedportions. Preferably, the die has a surface area at least as large asthe pattern of conductive elements to be included in a completeconnection component, and has a pattern of raised and recessed portionscorresponding to the conductive elements of at least one completeconnection component. The recessed areas of die 13 include relativelynarrow, elongated lead-forming areas 19 a connected to broad bus-formingregions 19 b. The bus-forming regions 19 b in turn are connected tointerconnect forming regions 19 c extending outwardly from the busregions to the edges of the die. The die 13 desirably also includesseveral additional recessed fiducial marker forming areas 19 d, justoutside of the area occupied by the other recessed areas. The particularpattern illustrated in FIG. 1a is an example only; the process of theinvention may be utilized for fabricating conductive elements of almostany shape, in almost any pattern. Backing element 14 has a flat surface14 a. The backing element and die are fixed to the opposing platens 30of a conventional reciprocating press actuated by a conventionalmechanism (not shown) such as a flywheel and clutch assembly, a fluidpower cylinder, screw mechanism, toggle mechanism or any other devicecapable of forcibly moving one or both of the forming elements towardone another.

A metal layer 10 having a first surface 11 and a second, oppositesurface 12 is placed between the backing element 14 and die 13. Themetal layer is provided as a continuous or semicontinuous strip of anymetal suitable for forming conductive leads such as copper, gold andalloys which can include either or both of these metals. While die 13 isin the retracted position shown in FIG. 1c, the strip is advanced to apredetermined position for engagement by die 13. The strip may beadvanced using known intermittent strip-feeding techniques commonlyemployed in the metalworking field.

After the metal layer has been positioned between the forming elements,the forming elements are moved towards one another, as by moving die 13linearly towards both the metal layer 10 and backing element 14(downwardly as seen in FIGS. 1c and 1 d), so that the die moves in adirection transverse to the metal layer to engage the metal layer. Thus,the forming elements forcibly engage the metal layer and deform it asshown in FIG. 1d. The raised portions 18 of the forming element 13 pressagainst the metal layer 10, squeezing and thinning the metal layerbeneath these portions 18 to form thin regions 16 of metal layer 10. Theexcess metal flows into recessed portions 19 of die or forming element13, and forms thick regions 15. The press then opens, moving the platens30 away from one another and leaving the metal layer or strip 10 withthe thick regions 15 and thin regions 16 seen in FIG. 1e. The thickregions 15, which will ultimately form the conductive elements andfiducial markers of a connection component, are precisely positionedrelative to one another. The precise spatial relationships between thethick areas 15 produced in the metal layer are built into die 13. Thereis no need for precise registration of die 13 with backing element 14.Further, the dimensions of each thick area 15 are precisely controlledby the die. Provided the die is engaged with sufficient force to fillthe recessed areas completely with the metal from the layer, the thickregions 15 will always have consistent dimensions. The thick regions 15formed on each stroke of the press provide a complete pattern of thickregions for forming a complete connection component. In addition, thethick regions formed on each stroke include interconnect regions 15 cconnecting the pattern formed on each stroke with the pattern formed onthe preceding stroke.

Because the backing element 14 is planar, the thick and thin areas ofthe metal layer 10 are formed as raised and recessed portions on thefirst or die-facing surface 11 of the metal layer. The second surface 12of the metal layer, facing toward the backing element during the formingprocess remains substantially planar.

The pattern of raised and recessed regions of die 13 is dictated by therequired pattern of conductive components in the connection component tobe made. However, to maximize the useful life of the die, the raisedportions 18 of the die should have as large a dimension in cross-sectionas possible. Thus, FIG. 1c shows that raised portions 18 have a largedimension w′, as compared to recessed portions 19 which have a smallerdimension w.

The die 13 and backing element 14 are preferably made of a rigid, hardmaterial such as a steel of the types commonly utilized for stamping andmetal-embossing tools. The recessed portions 19 of the forming elementor die 13 can be formed by a number of methods, including methodscapable of forming extremely fine features. Patternwise etching using aresist system and photographic developing system may be employed.Electron beam lithography or direct electron beam erosion may be used.Electrical discharge machining, mechanical engraving or any other knownmachining process may be utilized. The preferred die-making methods canform recessed features on the die smaller than the features achievableby conventional photochemical lead-forming processes, and can formcorrespondingly small conductive elements. In principle, there is nolower limit on the size of the recessed regions of the die. Thus, theprocess can be utilized to form conductive elements of essentially anysize. For example, the thick regions 15 which will form the conductiveelements 17 may have width w of about 40 microns or less, and typicallybetween about 20 and about 40 microns. The ratio of the depth d of eachrecessed portion 19 in the die to the width w of such recessed portion(the narrow dimension of the recessed portion in the plane of the diesurface) desirably is about 3:1 or less, and more preferably about 1:1or less, to facilitate release of the formed thick sections. Further,the walls of each recessed portion desirably slope outwardly away fromone another in the direction toward the die surface to furtherfacilitate release of the formed thick sections from the die. Ingeneral, the design practices known for metal coining dies used formaking other articles should be followed in design of the die.

In the next stage of the process, a dielectric base material is appliedon the first surface 11 of metal layer 10 so that the base materialintimately coats the first surface and fills the recesses between thickareas 15 of the metal layer. Base material 20 may be applied by applyinga flowable material onto the first surface as depicted in FIG. 1e. Theflowable material itself may be a dielectric material. Alternatively,the flowable material may be a conductive material which, when cured,forms a dielectric material. The dielectric material applied in thisstep will form the dielectric layer of a connection component.Therefore, the composition and thickness of the dielectric materialapplied in this stage of the process is selected to provide the desiredcomposition and thickness of the dielectric material in the connectioncomponent. Polyimide approximately 25 to 75 microns thick is a suitabledielectric material for use in many connection components. Flowablematerials may be applied by spin-coating. In spin-coating, the flowablematerial is deposited on the first surface in a globule adjacent thecenter of the surface, and the component is spun around an axisperpendicular to the first surface, causing the flowable material tospread over the surface. Where the embossing step is performed with alarge metallic layer such as a continuous strip used to form numerousconnection components, the step of applying the dielectric base materialmay be performed while the metal layer remains in this form. Thus,portions of a continuous strip incorporating the complete patterns ofthick and thin areas used to form leads for numerous connectioncomponents can be covered with the flowable material in a single spincoating operation. Alternatively, the metallic layer may be sprayed withthe flowable material, or the flowable material may be applied by meansof a brush or roller. Metallic strip 10 with the thick and thin regions15 and 16 may be advanced continuously or intermittently through such aprocess. After application of the flowable material, the flowablematerial is cured to form a continuous, coherent dielectric layer 20covering the first surface 11 of the metal layer. The resultingcomposite articles 28 are also in the form of a continuous strip, andremain connected to one another. As best seen in FIG. 1e, the raised orthick portions 15 of the metal layer are embedded in the surface of thiscontinuous dielectric layer 20.

Other methods of applying the dielectric layer may be employed as well.Thus, a sheet of dielectric material 20 may be laminated onto the firstsurface using conventional lamination techniques. In this case as well,the step of applying the dielectric base material desirably is performedso that the layer of dielectric material is in intimate contact with thefirst surface. For example, a thermoplastic dielectric material may belaminated to the first surface using heat and pressure to cause thethermoplastic material to flow into intimate engagement with the firstsurface of the metallic layer.

In the next stage of the process, metal is removed from layer 10 byexposing the composite article 28, including the dielectric layer andthe metallic layer, to a chemical treatment which attacks the metalliclayer but which does not substantially attack the dielectric layer. Forexample, where metal layer 10 is formed from copper or a copper-richalloy, an acid etching solution such as HCl and CuCl may be employed. Asseen in FIG. 1f, dielectric base layer 20 protects the first surface 11of the metal layer from the etchant and hence the etching occurs only atthe second surface 12 of the metal layer. Etching occurs nonselectively.The terms “nonselective” and “nonselectively,” as used in thisdisclosure with reference to a process for removing metal from a layer,mean that the removal process removes metal over a continuous regionsubstantially larger than the spacing between conductive elements to beformed. Stated another way, the etching process is not controlled toattack only specific areas in a specific pattern corresponding to themetallic elements to be formed. By contrast, a selective removal processremoves metal in a pattern corresponding to the negative of the patternof the desired metallic elements.

Numerous articles may be exposed to the etchant simultaneously. Forexample, where the articles are formed in a continuous strip or tape, asby performing the metal layer embossing or forming step and dielectricapplying layer steps on a continuous strip, the entire strip may beimmersed at once. Alternatively, a strip can be advanced continuallyinto and out of the etching bath. Where each article 28 in FIG. 1a beingtreated is a separate piece, numerous pieces can be placed into a commonetching bath, as by placing the parts within a basket or on a rack andimmersing the basket or rack in the etchant.

The etching process desirably is controlled so as to proceed at auniform rate over the entire surface of each component being treated.Known process conditions for enhancing the uniformity of an etchingprocess may be employed. For example, the etching bath may be gentlyagitated, and the articles being treated may be moved within the etchingbath, during the process to assure that the conditions of exposure tothe etchant are uniform over the second surface 12 of the metal layer.The planar second surface 12 of a metallic layer also tends to promoteuniform etching speed. As the etchant is agitated, or as the parts movethrough the etchant, the etchant can flow uniformly over the entiresecond surface 12, so that the average speed of etchant moving over thesurface during the process will be the same for all areas of thesurface. Stated another way, the pattern of thick areas 15 and thinareas 16 formed in the metallic layer has no influence on local etchingspeed.

As the etching process proceeds, metal is removed progressively from thesecond surface 12 of the metal layer. Eventually, the process reachesthe stage where depth of metal removal from the second surface is equalto the original thickness of the thin regions 16. At this point, thethin regions 16 have been entirely removed, as depicted in FIG. 1f,leaving metal only in conductive elements 17, at the locations occupiedby the thick regions 15 in the embossed or formed metallic sheet. Metalis left only in conductive elements and fiducial markers 17corresponding to the thick regions 15 of the metallic sheet formed bythe recessed regions 19 of the die.

At this stage, the etching process is arrested by separating the articlefrom the etchant. Preferably, the etchant is washed from the article. Aneutralizing solution may also be employed. For example, where theetchant is an acid medium such as HCL/CuCl solution, an alkalineneutralizing agent may be applied. Such a neutralizing step may befollowed by a rinsing step in distilled water, and by drying. Thecondition depicted in FIG. 1f, in which the conductive elements 17 havesurfaces exactly flush with the surface of the dielectric layer 20represents an ideal condition, which is achieved only when the etchingprocess is terminated immediately after the thin region 16 has beenetched away. In practice, it is desirable to leave the article in theetchant for a time slightly longer than that which is normally requiredto remove the thin regions. This will assure that all of the thinregions have been completely removed, even if there is some slightnonuniformity in the etching process. However, this will result in someloss of metal from the conductive elements, so that each conductiveelement is recessed slightly beneath the adjacent surface of thedielectric layer 20. To compensate for this loss, the depth of recessedportions 19 in the die, and hence the relief depth or height of thickportions 15 above thin portions 16 may be increased slightly. The endpoint corresponding to removal of the thin portions may be detected byobserving the article during the process either visually or with anautomated vision system. For example, a beam of light or otherelectromagnetic radiation at a wavelength transmitted by the etchantsolution and by the dielectric layer, but blocked by the metal layer maybe directed through the etchant and onto one surface of the articlewhile the article is disposed in the etchant. A photo detector isprovided on the opposite side of the article. When the etching processreaches the stage where the thin areas are removed, some of the radiantenergy will be transmitted through the article in the regions formerlyoccupied by the thin areas 16 of the metal layer. The signal from thephoto detector will indicate that the end point has been reached.Alternatively, in serial production, the required etching time can beestablished by trial and error, and once established can be maintainedprovided that the etching conditions are maintained substantiallyconstant. After the etching step is completed, the article 28 includesconductive elements 17, including leads 17 a connected to bus sections17 b and fiducial markers 17 d (FIG. 1g) embedded in the dielectriclayer 20. The bus sections 17 b of adjacent articles in the strip areconnected together by interconnect 17 c.

After completion of the etching step, gaps or apertures 21 are formed inthe dielectric layer in registry with leads 17 a. The conductiveportions may then be electroplated with additional metals to provideproperties such as corrosion resistance, fatigue resistance and ease ofbonding. For example, if the leads are formed from a copper alloy, theymay be overplated with gold. Preferably, a layer of a barrier metal suchas nickel adapted to prevent interdiffusion of gold and copper isapplied before the layer of gold. Plating current may be conducted toall portions of the metallic structure by means of the conductive busstructures 17 b. Also, the plating process may be performed on numerouselements in the tape or strip simultaneously, using the conductiveinterconnects 17 c extending between the bus structures. At this point,the article 28 comprises a connection component ready for use. Theconnection component may be handled, stored and assembled tomicroelectronic components such semiconductor chips while remaining inthe continuous strip form. Following such attachment, the connectioncomponents may be severed from one another along cutting planes 57between adjacent connection components on the strip so as to separatethe assemblies from one another. Alternatively, the connectioncomponents can be severed from one another before adjoining to themicroelectronic elements. The leads can be bonded to contacts on themicroelectronic elements using processes as mentioned in theaforementioned 94/03036 publication. Fiducial markers 17 d may be usedto align the microelectronic component with the connection component as,for example, by detecting the positions of the fiducial markers 17 d anddetecting the positions of features on the microelectronic element usinga robotic vision system and bringing the microelectronic element intoregistration with the connection component. As discussed in theaforementioned '036 publication, a bonding tool is engaged with eachlead and forces the lead downwardly into one of the openings orapertures 21 towards the microelectronic element. In this process, theend of each lead attached to bus structure 17 b is broken, therebydetaching the lead from the bus structure. To facilitate such breakage,leads 17 a may be provided with frangible sections (not shown) having asmaller width than the remainder of the lead. The frangible sections maybe performed by providing narrowed sections in the lead-forming recessedregions 19 a of die 13.

A process in accordance with a further embodiment of the inventionutilizes a die or first forming element 113 having a different patternof recessed areas 119. The recessed areas include a plurality of curvedlead-forming recessed regions 119 a, having recessed tip-end formingregion 119 b at one end of each lead forming region 119 a and a terminalend forming region 119 c at the opposite end of each lead formingregion. Lead forming regions 119 a are formed with a triangular crosssection similar to the cross section discussed above with reference toFIGS. 1b through 1 d, with walls sloping outwardly away from one anotherin the direction toward the die surface. The tip end forming regions 119b are conical, with steeply sloping, inwardly tapering walls. Each ofthe terminal end of forming regions 119 c is generally cylindrical andhas a first depth d1 from the raised surface 118 of die 113. Acylindrical post-forming region 119 d extends into the die from eachterminal end forming region 119 c, to a depth d2 from surface 118.Post-forming regions 119 d desirably have the minimum draft anglerequired to facilitate release of the metal part from the die afterforming, as discussed above. The depth of terminal end forming regions119 c is greater than the depth of tip end forming regions 119 b andgreater than the depth of lead forming regions 119 a. Thus, the dieincludes recessed regions having various depths. Die 113 also hasfiducial region forming recesses 132 outside the region occupied by theother recesses. The backing element or second forming element 114 usedin this process has recessed regions 121 (FIG. 2b) formed at spacingscorresponding to the spacings of tip end forming regions 119 b.

In the process, a copper or other suitable metallic strip or sheet 110is advanced between the die 113 and the backing element 114 and the dieis forced against the metal sheet and backing element using aconventional press with platens 130. This action forms a pattern of thinregions 116 and thick regions 115 in the metallic sheet 110. The thickregions include lead regions 115 a corresponding to the lead-formingregions 119 a of the die. In the manner discussed above, the leadregions 115 a project outwardly from the first surface 111 of metallicsheet 110. The thick regions 115 further include tip end regions 115 b.These regions project outwardly from the first surface 111 in the areascorresponding to the recessed regions 119 b of the die, and also bulgeoutwardly from the opposite, second surface 112 of the sheet in theareas corresponding to the recesses 121 of backing element 114. Thethick regions 115 further include terminal end regions 115 c and postregions 115 d projecting out of the first surface 111 of the sheet todifferent depths in accordance with the different depths of the recessedregions in the die. The thick regions further include fiducial regions(not shown) corresponding to the fiducial region forming recesses 132 inthe die.

This process does require control of registration between the die andthe forming element. However, the registration required is less precisethan that which would be required in a set of matched stamping dies toform features of a comparable size. Thus, recessed region 121 must bealigned with recessed region 119 b in order to form a common thickregion 115 b. However, the recessed region 121 on the backing elementneed not be exactly centered in recessed region 119 b on the die.Registration between these elements may be maintained in the mannernormally used to maintain registration between matched forming elementsin the metal working art. For example, the press may be arranged tomaintain very precise registration between platens 130. The dies andbacking element may be positioned and adjusted on the platens until thedesired registration is achieved. Once set, the registration will bemaintained.

In the manner discussed above, a dielectric layer 120 is applied overthe first surface 111 of the metal sheet. The dielectric layer 120 has afirst or top surface 127 remote from metal sheet 110 and a second orbottom surface 129 contiguous with the top surface 111 of the metalsheet. Here again, a base material is applied in such a manner so as toform a dielectric layer in intimate engagement with the metal sheet 110and filling in the regions around the raised or protruding elements 115on the first surface of the metal sheet. In this embodiment, however,the dielectric material desirably does not form a strong chemical bondwith the metal of the sheet. The sheet may be pretreated with arelease-promoting material such as a fluoropolymer or silicone beforeapplication of the dielectric material. Alternatively, the dielectricmaterial may be a thermoplastic such as a polyolefin applied bylamination.

Before etching, spots 131 of a bondable alloy such as a gold-tin orother eutectic bonding material or a solder are applied on the bottomends of tip end structures 115 b. Once again, a barrier metal (notshown) may be applied to prevent undesired interaction between thematerial of the metal sheet and the bonding alloy. The selective spotapplication process may be a plating process using conventionalphotoresist applied and photographically developed on second surface 112in registration with the pattern of tip end regions 115 b on the metalsheet. Because the metallic sheet 110 is continuous at this stage of theprocess, the metallic sheet can be used to conduct plating current toall of the tip end regions 115 b.

After the photoresist is removed, the metal sheet is etched again, inthe manner described above. Here again, the etching proceeds from thesecond surface 112 of the metallic sheet. The projecting portions of tipend regions 115 b beneath spots 131 are largely protected from theetchant by the spots. However, some undercutting around the edges mayoccur. Here again, the etching process is continued until the thinregions 116 are removed. However, the etching process is arrested beforethe thinnest ones of the thick regions 115 are removed, i.e., beforelead regions 115 a are removed. This leaves the article with numerousindividual, separate leads 135, unconnected to one another, on thebottom surface 129 of dielectric layer 120. Each lead has a tip endregion 117 b corresponding to the thick portion 115 b of the metalsheet, a terminal end portion 117 c corresponding to terminal endregions 115 c of the metal sheet and a flexible lead portion 117 aextending between the tip end and the terminal end. Each lead also has apost 117 d extending upwardly into dielectric layer 120, towards thefirst surface 127.

The terminals ends 117 c are relatively strongly held in the dielectricmaterial by posts 117 d. The tip ends 117 b of the leads are onlyloosely held in the dielectric material because the tip ends haveoutwardly tapering sides. Likewise, leads 117 a, having outwardlytapering sides defining a triangular cross section, are only looselyheld by the dielectric materials. By contrast, the terminal ends 117 care more firmly held in the dielectric by posts 117 d extending deeplyinto the dielectric. Holes or apertures 125 are formed in the dielectriclayer 120 from the first surface 127 of the dielectric, in registrationwith posts 117 d. The fiducial markers formed in the process may be usedto provide registration for forming holes 125. Holes 125 expose tips ofposts 117 d at the first surface 127 of the dielectric layer 120. Abonding material 137 such as a solder or other metallic bonding materialmay be applied to the tips of the posts. This further anchors the posts117 d and the terminal ends 117 c of the leads. The connection componentis then severed from the strip.

A connection component discussed above with reference to FIGS. 2a-2 fmay be used in a process for connecting a microelectronic element astaught in U.S. Pat. No. 5,518,964. As further discussed in the '964patent, a microelectronic element such as a semiconductor chip or waferhaving contacts in a pattern corresponding to the tip ends 117 b of theleads is engaged with the tip ends and the tip ends are bonded to themicroelectronic component. The connection component and microelectroniccomponent are then moved away from one another, so as to detach the tipends 117 b of the leads from the dielectric layer 120 and bend the leadsinto a more vertically extensive configuration. Of course, a typicalconnection component used in such a process includes many more leadsthan are illustrated in FIG. 2f.

As shown in FIG. 3a, a die 213 may have recessed portions includinglead-forming portions 219 a of a constant depth, interrupted byfrangible element forming portions 219 b. The frangible element formingportions 219 b are recessed to a lesser depth relative to die surface218 than the lead-forming portions 219 a. Die 213 also has bus-formingportion 219 c, and terminal-forming portions 219 d of the same depth aslead-forming portion 219 a. Die 213 is used with a planar backingelement 214. The forming process yields a structure including thinportions 216, lead portions 215 a having a thickness substantiallygreater than the thin portions 216 and frangible element formingportions 215 b interrupting each lead-forming portion. The frangibleelement forming portions 215 b have a thickness greater than the thinportions 216 but less than the thickness of the lead-forming portions215 a. The thick portions of the sheet project from the first surface211 of the sheet, whereas the second surface 212 is planar. Afterforming, the sheet is provided with a dielectric layer 220 overlying thefirst surface 211. The sheet is then etched from the second surface,leaving leads 217 a, each having a frangible portion 217 b. An aperture221 is formed in the dielectric sheet, as by laser ablation, leaving theleads projecting across the aperture. Once again, the metallicstructures can be plated with a bondable material such as gold over abarrier layer. These leads can be connected to a microelectroniccomponent in the manner discussed in WO 94/03036. As each lead is bentdownwardly, each lead is broken at frangible section 217 b.

As shown in FIG. 4a, forming elements 313 and 314 may be provided with aprojection 301 on one forming element matching with a recess 302 on theopposite forming element. The die and forming element are used inregistration with one another, so that projection 301 is aligned withrecess 302. These mating features form generally cup-shaped features 304in the metallic sheet. Additional recessed portions 306 surroundingrecesses 302 may be provided to form a collar around the cup-shapedfeature 304, whereas still further recessed portions 308 may be providedin one or both of the forming element to form elongated lead regionsprojecting from the collar 306. After application of a dielectric sheet320, the resulting structure has blind vias 317 a connected to leads 317b. Holes 325 may be formed through the dielectric layer from theopposite side of the dielectric sheet, so as to expose the ends of theblind vias 317 a for connection to further elements.

Numerous variations and combinations of the features discussed above canbe used without departing from the present invention. For example, it isnot necessary to apply a dielectric layer. Thus, the dielectric layermay be omitted, and the metal sheet may be etched from both sides byimmersing it into the etchant after the forming process. As thedielectric layer is not present to hold metallic elements formed fromthe thick regions, this process typically is used where the metallicelements formed from the thick regions of the sheet are relatively largeand are connected to one another so as to form a coherent metallicelement without any dielectric support. For example, lead frames of thetypes typically made by stamping can be made by processes according tothis alternative. Alternatively, if the pattern of thick areas on themetal sheet is discontinuous, the metal parts formed from the thickareas can be separated from one another by continued exposure to theetchant until the thin areas are dissolved away. The separated parts mayremain in the etchant bath for a short time after separation occurs, soas to form smooth surfaces on all areas of the parts. For example, theparts may fall away from the metal sheet and may be collected in ascreen or basket for removal from the etchant bath. In the processesdiscussed above, metal is removed nonselectively by a conventionaletchant. However, a reverse electroplating process may be used instead.In the reverse electroplating process, the article, including the metalsheet, is immersed in an electrolyte similar to an electrolyte used forplating. A metallic cathode is also immersed in the electrolyte. Anelectrical potential is imposed between the cathode and the sheet, sothat the sheet is positive with respect to the cathode. Material isplated from the sheet onto the cathode, thus removing the metal from thesheet. Such a reverse electroplating process can be conducted at arelatively rapid rate. The metal deposited on the cathode does not formpart of the finished component. Therefore, there is no need to limit theplating rate to avoid formation of asperities in the plated deposit.

The embossing step can be performed by forming elements other than thereciprocating elements discussed above. As shown in FIG. 5, a roller 425having raised and recessed portions 418 and 419, respectively, on itscircumferential surface 442 is shown in engagement with a metal layer410 supported by a flat backing element 414. The pattern of raised andrecessed portions on the roller 425 may form one or more completepatterns of the desired conductive elements to be formed. For example,where the connection components of FIG. 1g is to be formed, the roller425 may have one set of raised and recessed portions in the patternshown in FIG. 1b, or several sets in this pattern so that the patternrepeats itself around the circumferential surface of the roller 425.Roller 425 moves in a rotational direction 426 and a translationaldirection 427 across the metal layer 410 while backing element 414remains stationary so that the raised and recessed portions 418 and 419on the roller 425 are brought into engagement with the metal layer 410,producing thick and thin regions 415 and 416 in the metal layer 414.Alternatively, the roller may rotate while backing element 414 moves intranslation. Thus, backing element 414 may be a moving plate, belt orsimilar transporting device. In a further alternative, two rollers 525(FIG. 9) may be utilized to emboss the metal layer 10, either or both ofthem having recessed portions 519 in the pattern of desired metallicelements. In this arrangement, the metal layer 510 is embossed bypassing the metal layer between the rollers of forming elements 525 sothat the metal layer 510 is squeezed within a nip 529 defined by the twoforming elements. The rollers are rotated in feed directions 526 a and526 b so that their confronting surfaces move in a downstream direction(to the right as seen in FIG. 6). Thus, the rollers move the sheet 510downstream and draw the unembossed part 543 of the metal layer 510 intoengagement with raised and recessed portions on the circumferentialsurfaces of rollers 525 as the rollers rotate. FIG. 6 shows the thickand thin regions 515 and 516 formed by the rollers 525 on the embossedportion of the metal layer 510.

In the processes discussed above, the die forms thick regionscorresponding to one connection component, on each metal-engagingembossing operation of a press. However, each embossing operation mayform thick regions of more than one component, further adding to thenumber of components produced at a time. Less preferably, the elementsof only part of one component can be produced in each embossing step.Registration of elements formed during plural embossing steps would berequired to form a complete connection component.

In the processes discussed above, etching or reverse electroplating isemployed as the nonselective removal technique. These processes aregenerally preferred because they remove metal at a rapid rate and arecontrollable. However, other nonselective removal processes, such assputtering or abrading the metal layer may be utilized. In sputtering,atoms or ions bombard the metal layer and dislodge atoms of metal fromthe metal layer. This process normally is slower than etching. However,sputtering can be controlled precisely and therefore can be advantageouswhere very small conductive elements are to be formed. Further,sputtering can be used even with metals which are difficult to etch. Inabrading processes such as lapping, a fine abrasive material is movedagainst the metal layer, to wear away metal from the metal layer.Abrading is less desirable because the abrasive and metal particles cancontaminate the connection component produced.

The invention may utilize the embossing and nonselective removal stepsin conjunction with selective processes to form connection components.For example, the process discussed above in relation to FIGS. 2a-2 fuses a selective process in addition to embossing and nonselectiveremoval steps. In a further example, a layer of a first metal such ascopper 610 (FIG. 7) is embossed by a die and backing element asdescribed above, producing elongated thick regions 615 and thin regions616 on the first face 611 of the copper layer 610. The thin regionsinclude elongated strips 615 a. The backing element used in the processhas a flat surface. Thus, the second face 612 of the embossed copperlayer is flat. A photochemical resist is applied to the second face 612and developed to leave openings in a pattern on the second surface 612.A second metal such as gold is applied in the open regions byelectroplating to form gold components 647 on the second face 612 of thecopper layer 610. In this example, the gold is deposited so that thegold components overlap with the elongated thick portions 615 of thecopper layer 610. A polymeric base material or dielectric layer 620 isapplied to the second surface 612 as described above and the resultingassembly is etched from the first surface 611 to remove the thin regions616 of the copper layer 610. Since the copper is more easily etched thangold, the dielectric layer 620 is not required to protect the goldelements 647. The resulting leads include elongated strips of coppercorresponding to elongated strips 615 a, joined to gold strips 647. Aprocess in accordance with this aspect of the invention thus can formcomposite leads as taught in U.S. Pat. No. 5,679,194, the disclosure ofwhich is incorporated by reference herein. Before or after the etchingstep, apertures 621 are formed through the dielectric layer in alignmentwith the gold portions 647 of the composite leads. As taught in the '194patent, it is advantageous to bond the gold portions of the leads tochip contacts, as gold has superior fatigue resistance and bondability.The copper portion of the lead reduces the cost of the componentproduced.

In another example, metals of different embossing and/or etchingcharacteristics are used to form the metal layer which is embossed. FIG.8a shows a layered assembly of gold 750 and copper 751 as the metallayer 710. The gold 750 is more easily embossed than the copper 751 sothat the forming element 713 almost entirely displaces the gold inregion 752 beneath the raised portions 718 on the forming element 713,as seen in FIG. 1b. The copper in region 752 remains almost unaffectedby the forming element 713. After the embossing step, the thin regions716 of the metal sheet have relatively little gold. During the removingstep, any gold in thin regions 716 and all of the copper in the thinregions is removed whereas the gold in thick regions 715 remains asconductive elements.

The base material may be applied before the embossing step or subsequentto the embossing step, as discussed above. The base material need not bea dielectric material. For example, the base material may include ametal such as stainless steel or aluminum having different etching andembossing characteristics from a copper or gold working metal layer. Thelayered assembly may be embossed on a first surface facing away from thebase material, and subjected to a nonselective removal process. Theworking metal layer such as copper or gold is primarily deformed by theembossing step and the base metal layer is relatively undeformed. Achemical etchant which only attacks the working metal layer is thenutilized. The thick regions of the working metal remain as conductiveelements supported on the base metal. The conductive elements may beremoved from the base metal, as by applying a dielectric material andstripping the dielectric material from the base metal. Anotheralternative is to apply a base metal layer after the embossing step.

The processes discussed above illustrate use of the invention to formconnection components for semiconductors. However, the invention can beapplied to manufacture of other electrical components, including circuitpanels commonly referred to as circuit boards. The conductors of acircuit board may be formed from the thick regions of the metal sheet.Also, metallic components for non-electronic applications can be made byprocesses according to the invention.

Although the present invention has been described in considerable detailwith reference to certain preferred examples thereof, other versions arepossible. Therefore, the spirit and scope of the appended claims shouldnot be limited to the description of the preferred examples containedherein.

What is claimed is:
 1. A method of making a microelectronic package,comprising: (a) making at least one microelectronic component,comprising the steps of: (i) embossing a metal layer having a first faceand a second face by engaging said metal layer between a pair of formingelements and deforming said metal layer by engagement with said formingelements so as to form thick and thin regions of metal in said metallayer; (ii) removing metal from said thick and thin regions of metal insaid metal layer by a removal process which nonselectively removes metalfrom at least one face of said metal layer; and (iii) arresting saidremoval process after said thin regions of metal have been removed butprior to removal of said thick regions of said metal layer so that saidthick regions of metal remain as first metallic elements; and (b)assembling each of said at least one microelectronic component with atleast one microelectronic element.
 2. The method of claim 1, furthercomprising the step of forming a first layer of metal on said firstmetallic elements.
 3. The method of claim 2, wherein said step offorming a first layer of metal includes electroplating onto said firstmetallic elements a layer of metallic material different than themetallic material of said first metallic elements.
 4. The method ofclaim 2, further comprising the step of forming a second layer of metalon said first metallic elements, said first layer of metal comprising alayer of barrier metal to prevent interdiffusion of metallic materialbetween said first metallic elements and said second layer of metal. 5.The method of claim 1, wherein said step of making at least onemicroelectronic component comprises making a plurality ofmicroelectronic components in a continuous strip.
 6. The method of claim5, wherein said at least one microelectronic element comprises aplurality of microelectronic elements and said step of assemblingincludes assembling each of said plurality of microelectronic componentsof said continuous strip with each of said plurality of microelectronicelements to form a continuous strip of assemblies.
 7. The method ofclaim 6, further comprising the step of severing said assemblies fromone another after said step of assembling.
 8. The method of claim 1,wherein said metal layer comprises a metal layer of first metal and themethod further comprises depositing a second metal on said second faceof said metal layer of first metal.
 9. The method of claim 8 furthercomprising forming additional metallic elements, including applying aphotoresist to said second face of said metal layer of first metal andpatterning said photoresist.
 10. The method of claim 9 wherein saidadditional metallic elements are formed in contact with said firstmetallic elements formed from said metal layer.
 11. The method of claim10 wherein said steps of making said at least one microelectroniccomponent includes the step of applying a base material to said secondface of said metal layer, overlying said additional metallic elements.12. The method of claim 11 wherein said steps of making said at leastone microelectronic component includes forming apertures in said basematerial in alignment with said additional metallic elements.
 13. Themethod of claim 1 wherein said step of making at least onemicroelectronic component forms metallic elements having a width of lessthan 40 microns.
 14. A method of making a microelectronic package,comprising: (a) making at least one microelectronic component,comprising the steps of: (i) embossing a metal layer having a first faceand a second face by engaging said metal layer between a pair of formingelements and deforming said metal layer by engagement with said formingelements so as to form thick and thin regions of metal in said metallayer; (ii) removing metal from said thick and thin regions of metal insaid metal layer by a removal process which nonselectively removes metalfrom at least one face of said metal layer; (iii) arresting said removalprocess after said thin regions of metal have been removed but prior toremoval of said thick regions of said metal layer so that said thickregions of metal remain as metallic elements; (iv) applying a basematerial to said first face of said metal layer after said embossingstep so that a coherent layer of said base material intimately surroundssaid protruding thick regions of metal and so that said thick regions ofmetal in said metal layer remain as conductive elements embedded in saidbase material after said removing and arresting steps; and (b)assembling each said at least one microelectronic component with atleast one microelectronic element.
 15. The method of claim 14 whereinsaid step of applying a base material includes applying a dielectricmaterial.
 16. The method of claim 14, wherein said base materialcomprises a thermoplastic material applied by lamination.
 17. The methodof claim 14, wherein said steps of making at least one microelectroniccomponent includes the step of forming at least one aperture in saidlayer of base material in alignment with at least some of said metallicelements.
 18. The method of claim 17, wherein said step of making atleast one microelectronic component is performed so as to form saidmetallic elements as elongated leads and said step of forming said atleast one aperture includes forming apertures in alignment with saidelongated leads so that the leads extend at least partially across saidapertures.
 19. The method of claim 14 wherein said step of applying abase material is performed so that said thick regions of metal have aportion releasably adhered to said layer of base material.
 20. Themethod of claim 19 wherein said metallic elements have a first end fixedto said layer of base material and a second end which is releasable fromsaid layer of base material.
 21. The method of claim 19, wherein saidsteps of making one or more microelectronic components includes applyinga release-promoting material to said metal layer prior to the steps ofapplying a base material.
 22. A method of making a microelectronicpackage, comprising: (a) making at least one microelectronic component,comprising the steps of: (i) embossing a metal layer having a first faceand a second face by engaging said metal layer between a pair of formingelements and deforming said metal layer by engagement with said elementsso as to form thick and thin regions of metal in said metal layer; (ii)removing metal from said thick and thin regions of metal in said metallayer by a removal process which nonselectively removes metal from atleast one face of said metal layer; (iii) arresting said removal processafter said thin regions of metal have been removed but prior to removalof said thick regions of metal in said metal layer so that said thickregions of metal in said metal layer remain as metallic elements; (iv)said step of embossing being performed so as to form thick regions ofmetal including thick regions of metal having different thicknesses, andwherein said removing step is arrested before the thinnest of said thickregions of metal have been removed so that said thick regions of metalremain as metallic elements, said metallic elements having differentthicknesses; and (b) assembling each said at least one microelectroniccomponent with at least one microelectronic element.
 23. The method ofclaim 22 wherein said step of making at least one microelectroniccomponent includes applying a base material to said first face of saidmetal layer so as to form a coherent layer of base material and formingan aperture in said base material in alignment with at least one of saidmetallic elements.
 24. A method of claim 23 wherein said step ofembossing is performed so as to form said metallic elements as elongatedleads, at least one of said elongated leads extending across saidaperture.
 25. The method of claim 24, wherein said step of assemblingincludes forcing said at least one of said elongated leads downwardlyinto said aperture.
 26. The method of claim 25, wherein one of saidthick regions comprises a frangible section of one of said elongatedleads and said elongated lead having said frangible section is forceddownwardly so as to break said frangible section.
 27. The method ofclaim 26, wherein said step of assembling includes bonding saidelongated leads to contacts on said at least one microelectronicelement.
 28. The method of claim 24, wherein the step of assemblingincludes applying spots of a bondable alloy to said elongated leads. 29.The method of claim 28, wherein said step of applying spots of bondablematerial includes applying a photoresist and patterning said photoresistto form said spots of bonding material on said elongated leads.
 30. Themethod of claim 28, wherein said step of assembling includes bondingsaid spots of bondable material to contacts on said at least onemicroelectronic element.
 31. A method of making a microelectronicpackage, comprising: (a) making at least one microelectronic component,comprising the steps of: (i) embossing a metal layer having a first faceand a second face by engaging said metal layer between a pair of formingelements and deforming said metal layer by engagement with said elementsso as to form thick and thin regions of metal in said metal layer, atleast some of the thick regions of metal having tapering sides; (ii)removing metal from said thick and thin regions of metal in said metallayer by a removal process which nonselectively removes metal from atleast one face of said metal layer; (iii) arresting said removal processafter said thin regions have been removed but prior to removal of saidthick regions of metal so that said thick regions of metal remain asmetallic elements, (iv) said steps of embossing, removing metal andarresting said removal process forming metallic elements includingtapering sides; (v) applying a base material to said first face of saidmetal layer after said embossing step so that a coherent layer of saidbase material intimately surrounds said thick regions of metal and sothat said thick regions of metal remain as conductive elements embeddedin said base material after said arresting step, said tapering sidestapering outwardly toward a surface of said layer of base material; and(b) assembling each of said at least one microelectronic component withat least one microelectronic element.
 32. The method of claim 31,wherein said step of embossing is performed so that said metallicelements each have an elongated portion, a tip-end, and a terminal end,said tip-end having a width greater than a width of said elongatedportion.
 33. The method of claim 32, wherein said tip-ends are formedhaving tapering sides.
 34. The method of claim 32, wherein said steps ofmaking at least one microelectronic component includes applying spots ofbondable alloy to said tip-ends of said metallic elements.
 35. Themethod of claim 34, wherein said step of assembling includes engagingsaid tip-ends with contacts of said at least one microelectronicelement, said contacts being in a pattern corresponding with saidtip-ends, and bonding said spots of bondable material to said contacts.36. The method of claim 35, wherein said step of assembling furtherincludes the step of moving said at least one microelectronic componentand said one or more microelectronic elements away from each other sothat said tip-ends are detached from said base material.
 37. A method ofpackaging a microelectronic element, comprising: (a) making at least onemicroelectronic component, comprising the steps of: (i) embossing ametal layer having a first face and a second face by engaging said metallayer between a pair of forming elements having recesses and projectionsin registrations and deforming said metal layer by engagement with saidelements so as to form thick and thin regions of metal in said metallayer; (ii) removing metal from said thick and thin regions of metal insaid metal layer by a removal process which nonselectively removes metalfrom at least one face of said metal layer; and (iii) arresting saidremoval process after said thin regions of metal have been removed butprior to removal of said thick regions of metal so that said thickregions of said metal layer remain as metallic elements; and (b)assembling each of said at least one microelectronic component with atleast one microelectronic element.
 38. The method of claim 37 whereinsaid steps of embossing and removing are performed so as to formmetallic elements having cup-shaped features each having an open end atsaid first face of said metal layer and a closed end at said second faceof said metal layer.
 39. The method of claim 38, wherein said steps ofembossing and removing are performed so as to form a collar-shapedportion at said first face surrounding said open end of each of saidcup-shaped features.
 40. The method of claim 39, wherein said basematerial is applied to said second face of said metal layer so that saidclosed end of each said cup-shaped feature is embedded in said layer ofsaid base material.
 41. The method of claim 40 wherein said steps ofmaking at least one microelectronic component includes forming anaperture in said base material in alignment with each said closed end ofsaid cup-shaped feature.
 42. The method of claim 41 wherein said step ofassembling includes electrically connecting said closed end to said atleast one microelectronic element.